Comparison · Igneous Rocks
Granite vs Porphyry
Granite and Porphyry are easy to confuse because both are igneous rocks. Both sit near Mohs 6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Granite and Porphyry
- Both sit near Mohs 6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Hold a thin edge to the light: Granite is opaque, Porphyry is Opaque.
- They overlap in gray, but Granite also comes in pink, white, and black and Porphyry also comes in purple, red, and green.
Granite vs Porphyry properties
| Property | Granite | Porphyry |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6.5 | 5–7 |
| Luster | vitreous | Dull to vitreous |
| Streak | Variable; test individual minerals | — |
| Transparency | opaque | Opaque |
| Specific gravity | 2.7 | 2.6–2.8 |
| Crystal system | varies | — |
| Common colors | Pink, Gray, White, Black | Purple, Red, Gray, Green |
| Rarity | common | common |
| Typical specimen value | $1–$50+ | $1–$75+ |
Which is more valuable?
Typical specimens of Granite and Porphyry trade in a similar range, around $10.
About Granite
Granite is a coarse-grained igneous rock composed mainly of quartz, feldspar, and mica. It's one of the most common rocks in Earth's continental crust.
About Porphyry
Porphyry is a textural term for any igneous rock that contains large, visible crystals called phenocrysts embedded in a much finer-grained groundmass, rather than a description of a specific mineral composition. The texture records a two-stage cooling history, slow crystal growth at depth followed by rapid cooling near or at the surface. Porphyry can be volcanic or shallow intrusive and of almost any composition, from basaltic to rhyolitic.
Granite vs Porphyry FAQ
Is Granite the same as Porphyry?
No. Both are igneous rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Granite from Porphyry?
Both sit near Mohs 6.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Hold a thin edge to the light: Granite is opaque, Porphyry is Opaque. They overlap in gray, but Granite also comes in pink, white, and black and Porphyry also comes in purple, red, and green.
Which is harder, Granite or Porphyry?
Granite is harder: Mohs 6.5 against Mohs 5–7 for Porphyry.
Which is more valuable, Granite or Porphyry?
Typical specimens of Granite and Porphyry trade in a similar range, around $10.
